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This is just a curiosity post. Does anyone have flowbench figures for the Gurney/Weslake or Gurney Eagle heads? I'm just curious to find out how they perform compared with modern SBF heads like the AFR 185s or equivalent.

They are eclipsed by variants like the 185s and others. And, bear in mind, there are shops that can improve the 185s with CNC porting while still keeping port velocity high. Not enough flow still - step up to 205 or 225s.

There are some figures running around on the forum on the GW heads though, showing them outflowing AFR heads. But the post didn't take into account the street/non-emissions 185 AFR heads and that things can be done to the AFR heads to improve them still further.

Fact is, you can get more flow for lower cost using a late model performance head.

I was pretty sure that many of the modern heads would outperform the original GW heads. Curiosity getting the better of me, I was wondering if anyone had some specifications so that I could compare them.

I'm also curious about the original cam grinds.

My goal is to equal the power of the '69 Gulf cars with a 331. The slight increase in displacement will allow for a slightly milder setup for the same peak power and with EFI and a good computer, the engine would be pretty friendly on the road while still being able to headbutt the horizon with enthusiasm.

After some surfing around the Net, I found this on the GW heads. Sounds like a completely stock, unported pair of heads.

Just in case you're interested.

Stew

*******************
The heads tested belonged to a friend and when we pulled the valves out,
it was apparent these heads were not going to live up to their potential.
It's not because of anything wrong in the basic design but rather they
didn't appear to have been finish-machined. There's a huge step at the
short side radius that's sharp enough to cut your finger on. Bob said
blending that area in would be worth a bunch of CFM and power. He guessed
the intakes wouldn't flow over 225 CFM but that, with some work, they
would pick up to 300+ CFM. The flow bench tells the tale. Same set up
as before (28" H20 pressure drop, clayed inlet radius, no pipe on the
exhaust):

> After some surfing around the Net, I found this on the GW heads. Sounds like
> a completely stock, unported pair of heads.

Those flow numbers you quoted were from me. They were indeed from a completely
stock set of heads, as purchased from Gurney. I also believe they were only
partially finished machined. That step I mentioned looks like a real flow
killer. With that removed and a good bowl porting and valve job, those heads
should do much better. I wouldn't be surprised to see them as good as the
majority of modern Windsor heads but that remains to be seen.

There were a series of Gurney heads. There were the Gurney AAR-designed MK1
heads that were cast by Alcoa and found to have insufficient thickess
is a few spots. The Weslake-designed heads went through several revisions
resulting in MKII, MKIII, and MKIV Gurney-Weslake heads. Most were cast
at William Mills in England. The MKIII was a minor revision of the MKII
race head and the MKIV was a narrowed version made to better fit into
Mustangs and Cougars. The MKIV heads were renamed Gurney-Eagles after
Gurney took over manufacturing responsibilities. That's the version we
tested. There was also a 3 valve pushrod head developed by John Miller
at AAR. The first set suffered from coolant passage problems that allowed
steam pockets to form and were subsequently revised to fix that problem.
I don't know that much about the 3 valve heads but I don't think they were
the success the Gurney-Weslakes were. This wasn't because of anything
fundamentally wrong with the heads (they out-flowed the Weslakes) but
rather there wasn't a racing venue for them (Can Am went big block, Ford
went Boss 302 in Trans Am, Formula 1 went V-12 and Cosworth, Indy was turbo
Offy and Ford 4 cam, Ford pulled out of Endurance racing, etc.) so I don't
think they were developed or raced to any menaingful degree.

Detomaso also had a version of the the Weslake heads prototyped. Some
pictures of the Detomaso heads, along with pictures of the MK-IV heads
we flow tested, can be seen on my website at:

Notice the modern chamber shape of the Gurney-Weslake heads, along with
the intake runner optimized for independent runner manifolding. BTW, my
buddy Bill had Harland Sharp prototype a set of roller rockers for his
Gurney-Weslake heads. The G-W's have a shaft mounted rockers with
different intake and exhaust rockers.

> I was pretty sure that many of the modern heads would outperform the original
> GW heads. Curiosity getting the better of me, I was wondering if anyone had
> some specifications so that I could compare them.

We're hoping to get a pair of Gurney-Weslake heads to David Vizard for
analysis and a port job. Vizard knew the guy at Weslake who was
responsible for the Gurney head development. According to Vizard, one
of the Alan Mann-prepared Falcon's was making over 500 RWHP from a 302
in the late 1960's. Pretty impressive for the time. Vizard would like to
do an article on the Gurney-Weslakes, comparing them to modern heads to
see just how far we've really come.

> Which is to be expected given 40 years of technology.
> But for their time, the GW heads were awesome.

Just because they are old, doesn't mean they can't make modern power.
I've yet to test a set of Windsor heads that betters the 25 year old Ford
Motorsport high port heads. Those old canted valve heads are still
outstanding. My small port C302B street heads flow 331 CFM intake and
228 CFM exhaust (without the aid of a pipe) at 0.6" lift on a conservative
bench. That's better than the AFR 225cc race Windsor heads in the graph
above despite having smaller port volumes (note the AFR claimed exhaust
flow numbers are quoted with the aid of a pipe, without the pipe expect
to see 20-30 CFM less).

I was pretty sure that many of the modern heads would outperform the original GW heads. Curiosity getting the better of me, I was wondering if anyone had some specifications so that I could compare them.

I'm also curious about the original cam grinds.

My goal is to equal the power of the '69 Gulf cars with a 331. The slight increase in displacement will allow for a slightly milder setup for the same peak power and with EFI and a good computer, the engine would be pretty friendly on the road while still being able to headbutt the horizon with enthusiasm.

Stew

Hi, Stew.

If you haven’t already purchased your reciprocating assembly and had your block work done, please seriously consider the M-6010-BOSS302 block, punched-out to a 4.125-inch bore. With your 3.250-inch stroke, this will give you 347.47 cubic inches (5.694 liters), which is almost identical to the extremely popular “347” combination (like the M-6013-B347/C347). The latter uses a 4.030-inch bore and a 3.400-inch stroke for 346.95 cubic inches (5.685 liters).

The bigger bore provides more of a power increase than the simple increase in displacement suggests. First, it unshrouds the valves, making your heads more efficient: the better your engine breathes, the more power it makes.

And just so we’re on the same page: in the 1970s, NHRA Pro Stock racers like Bob Glidden campaigned the 351C -- using blocks that had been sleeved (rather elaborately: the process involved furnace-brazing and stress-relief) and bored to 4.080 inch. If they could have gone larger, they would have – not so much for the displacement as for the unshrouding of the valves.

The other benefit of a larger bore is a piston having greater surface area. Assuming a perfect seal between the piston and the cylinder, and a perfectly round cylinder:

If you apply 1000 psi to each (for instance, during the combustion event), the force translated by the 4.030-inch diameter piston is 12,566 pounds; the force translated by the 4.125-inch diameter piston is 13,364 pounds (nearly 8 percent more). Of course, if you’ve got the bucks, the M-6010-F302 block will shave about 70 pounds and let you go to a 4.155-inch bore!

Alternatively, the M-6010-S302 block weighs a few pounds more, but gives you an extra half inch of deck height to play with – room for a slightly longer rod and a much more “normal-looking” (and robust) piston!

There are a variety of ways to do EFI with the slightly-taller block, but the easiest is probably to use spacers between the heads and the intake; everybody seems to have his or her own idea about how to space an intake, so I’ll skip that – except I must mention this: don’t forget to add the thickness of the spacer (and gaskets) to the length of your intake runners when you’re getting a custom camshaft ground. Later in this message, I’ll get to what I mean by “custom camshaft.”

You want to use a 3-ring stack (compression, wiper, oil) on the street. Ford Racing Parts claims their M-6013-B347/C347 uses a set of 1.090-inch tall pistons, each featuring a 1/16-inch, 1/16-inch, 3/16-inch ring stack. The set of pistons is part number M-6108-C347. The distances between the rings must be incredibly thin! Even at that, it seems the top ring is going to take a severe beating from the heat.

The “assembled height” (cold) of a 3.400-inch stroke, a 5.400-inch connecting rod, and a 1.090-inch piston is 8.190 inches. Working backwards, if you limit yourself to an “assembled height” (cold) of 8.190 inches and you use a 5.400-inch connecting rod with a 3.250-inch stroke, your piston is 1.165 inches tall.

For a 3-ring stack, that’s still an awfully short piston -- imho -- however, it offers a lot more room for the rings than what Ford is selling. If you shorten the rod to 5.315 inches (a common aftermarket length for the SBF; the same length as the D0ZX-6200-A “302 Boss, 9000 rpm, competition-only” rod from Ford’s Off Highway Parts program), it gets even better: your piston is 1.250 inches tall -- which will allow the use of canted valves.

With a 3.250-inch stroke, the 5.400-inch rod will give you a rod:stroke ratio of 1.6615:1; the 5.315-inch rod will give you a rod:stroke ratio of 1.6354:1. For comparison, the 351C (including the Boss 351) has a rod:stroke ratio of 1.6514; the 350 SBC has a rod:stroke ratio of 1.6379:1. The 410 and 428 FE big blocks from Ford each has a rod:stroke ratio of 1.6304:1, and the 400 SBC has a rod:stroke ratio of 1.4840:1.

Any one of the foregoing engines can be configured to provide both a reasonably smooth idle and a broad powerband that is easily accessible.

To give you an idea of the potential of a small-bore 347 that has the wrong camshaft, check out http://popularhotrodding.com/enginem...ck/0506em_347/ but remember that’s an engine purpose-built to make good power numbers on pump gas during only a few pulls on a dynamometer. One look at the lift indicates the cam isn’t intended for street use -- and the insane valve spring pressures simply confirm this.

On the other hand, it says you can make 93.2 horsepower per liter using racing gasoline or E85, with a 10.6:1 compression ratio.

For something a lot more streetable -- and featuring EFI -- check out http://www.trickflow.com/articles/st...t_st_4_347.asp. The power curve looks a little strange, but you’re looking at a pretty mild, generic small-bore 347 that will probably run all day on 87PON petroleum gasoline (though you might have to retune for crappy gas), and crank out 70.9 horsepower per liter.

For what it’s worth, that translates to well over 500 horsepower at the flywheel. That engine uses the 5.315-inch connecting rod with a 3.400-inch stroke, giving it a rod:stroke ratio of 1.5623:1 -- and though the camshaft will produce a significant lope, it is streetable.

Oh, here’s another link: http://truckinweb.com/brandpages/for...med/index.html. The engine is another small-bore 347, and it makes “only” 380 horsepower -- at only 4600 rpm! It’s carbureted, but still: pretty freaking impressive for pump gas and natural aspiration. Oh, and none of the above figures included laughing gas: “Ride too slow? Add a little N20 -- and away you go!”

http://www.jegs.com/ offers carbureted and EFI versions of the small-bore 347, in 9.5:1 compression with horsepowers to 435, and torques to 425 lbf.

But if you want to get the best output, I think the 4.125 x 3.250 combination is the way to go -- especially with the 5.315-inch connecting rod. And if you need even more punch, boost the stroke to 3.400 inches for 363.5 cubic inches (5.957 liters)! Vrooom!

That's the only combustion chamber shape I've seen and is the one shown in the magazine articles of the day. It was a revision to the MKII design but I don't know if there were any later revisions. Also, it's not uncommon for heads to have their chambers altered for domed pistons.

I'm not a GT40 nut, but have an interest in the Gurney-Weslake heads and their down-draught configuration, while googling around I noticed Knight Race engines also do a re-make of this legendary head......looks like they have done a good job to me, see the pics and info in the attached link.......nothing to do with me by the way, I can assure you I'm in no way related!

I would be interested to know what sort of power anyone is are now making on a 305 (5 litre) block fitted with GW heads, last I heard was 520bhp???......which is over 100bhp per litre, which is pretty impressive, even today!.......

please forgive my ignorance, whats the bore and stroke of a 305 block?........also - whats the valve angle of the GW heads?

Gurney/Westlake were of course on the right track with their cylinder heads. The only deficiencies the had was they went with 2 valves instead of 4. The standard 80 degree V8 head cannot compare with GW heads. The only way to improve on the GW head is to go Cosworth. Replacement aftermarket heads offer only minor improvement. ranger jim

Hi, an interesting note is Gurney and Weslake did make multi 3-4 valve pushrod heads for the sbf+sbc engines that made some very good power #'s.

I have heard but not been able to confirm Weslake did make a test 4v sbf pushrod version baised off there sbc design also. Many dont know it but the 32 valve Dominion and Arao version heads are modeled after the old weslake design, just with there own take on using stock type int and exh setups.